Various brushless motors having high controllability and reliability over a wide rpm range have been used as motors for rotationally driving disks on which information is recorded and reproduced. Such brushless motors are disclosed in, for example, JP2002-262540A, JP08-214487A, JP2004-236390A, and so on.
As shown in FIG. 5, such a brushless motor is made up of a stator 52 serving as a non-rotating portion fixed to a stator base 51 serving as a base member, and a rotor 54 serving as a rotating portion integrally rotating with a rotating shaft 53.
The stator 52 includes a substantially cylindrical bearing 55 for rotatably holding the rotating shaft 53 of the rotor 54, a cylindrical bearing housing 56 placed vertically on the stator base 51 with the bearing 55 press-fit into the bearing housing 56, a thrust plate 57 which is disposed in a hole 51a formed on the stator base 51 and comes into contact with the rotating shaft 53 from the proximal end of the rotating shaft 53 (the end opposite to the end where a rotated object is loaded) in a thrust direction to rotatably support the rotating shaft 53, a thrust cover 58 for holding the thrust plate 57 from below, and a winding assembly 61 composed of a core 59, being fit onto the bearing housing 56, a coil 60, and so on.
As described above, the brushless motor configured thus includes the thrust plate 57 which receives the rotating shaft 53 in the thrust direction (to be specific, from the end opposite to the end where a disk is mounted as a rotated object) and the thrust cover 58. The thrust plate 57 and the thrust cover 58 may be integrally formed.
The thrust cover 58 is fixed as follows:
In a brushless motor disclosed in JP2002-262540A, as shown in FIG. 5, the thrust cover 58 is a closed-end cylinder. In the assembling process, the upper part of the thrust cover 58 is fit into the bottom of the bearing housing 56 as indicated by the virtual lines of FIG. 5. In the brushless motor, the bearing housing 56 is integrally formed with the stator base 51 by burring.
In a brushless motor disclosed in JP08-214487A, as shown in FIG. 6, a thrust cover 71 is formed like a disk. The outer periphery of the thrust cover 71 and a stator base 73 (to be specific, a hole surrounding section 73a of the stator base 73) are fixed by welding or bonding such that the thrust cover 71 closes the bottom of a space in a bearing housing 72 where a thrust pad 74 and a bearing 75 are stored.
In a brushless motor disclosed in JP2004-236390A, as shown in FIG. 7, the bottom of a cylindrical bearing housing 81 has a resin thrust cover 82 molded by outsert molding.